WASHINGTON - When the battle for Libya seemed to be slipping into stalemate in late April, the British, French and Italians sent “military advisers,” a phrase that to much of the world suggests the first step on the slippery slope to ground forces.

President Obama offered up his administration’s favorite weapon: armed Predator drones.

The difference said much about the Obama way when it comes to intervening in armed insurgencies - and his comfort in letting someone else lead the intervention. Caught between two searing experiences in the past two decades - America’s failure to do anything in Rwanda and its insistence, over the objection of key allies, on going into Iraq eight years ago - Mr. Obama has spent much of the past month experimenting with a third way.

In Libya, he has committed the United States, but only from the air and only from afar. The Europeans, and some of Mr. Obama’s political opponents, sense a lack of commitment. Inside the White House, the opposite argument is made - that after a bruising decade of misadventures, the United States is preserving American power for the moments when truly vital interests need to be protected, while teaching the rest of the world that it will have to police its own backyards.

But is this any way to fight a war? That depends on what one considers to be the objective: protecting the population, ousting Colonel Muammar el-Qaddafi - whom President Obama has said must go - or making a broader point, around the world, that the United States has once again entered a deeply nonideological, measure-the-cost phase in its foreign policy. Secretary of Defense Robert Gates, soon to leave Washington, has observed more than once that the question the Bush administration asked far too infrequently before its military interventions was “And then what?” It is a lesson Mr. Obama has clearly internalized - and, some of his critics say, overlearned.

European officials lament that this is the first NATO operation since the creation of the alliance a half-century ago in which the United States has declined to take the lead. Some former Clinton administration officials have uttered similar concerns, along with Republican critics like Senator John McCain, who made his point in late April by flying into Benghazi, Libya. (His enthusiasm is apparently not broadly shared in the Republican Party: At the same moment Mr. McCain was cheering on Colonel Qaddafi’s opponents, Representative Michele Bachmann of Minnesota, the Tea Party favorite weighing a run for the presidency, declared that the president was foolish to support reb-els who include “elements of Al Qaeda in North Africa and Hezbollah.”)

Yet the question may be not whether the United States leads, but whether it puts its credibility on the line by seeming to enter the conflict half-heartedly. “We either have to do a lot more - and the Predators were a step in that direction - or go for a cease-fire and live with the fact that Qaddafi could be in place for some time,” said Richard N. Haass, the president of the Council on Foreign Relations.

Mr. Haass is making the case that President Obama is violating the Powell Doctrine: If you elect to use the United States military, you must do so with such overwhelming force that there is no doubt of the outcome. The term dates back two decades, to General Colin L. Powell’s strategy for the 1990-91 gulf war. The White House seems intent on creating an Obama Corollary: The Powell Doctrine does not apply when the United States joins a coalition with countries that have a larger stake in the outcome than Washington does.

“We did lead - we cleared the way for the allies,” Antony Blinken, Vice President Joseph R. Biden Jr.’s national security adviser and a key player in the Libya debate, said in mid- April. “But real leadership is successfully encouraging others to step up to their responsibilities. We’ve talked for years about burden-sharing, and either we would not let other countries act, or they wouldn’t or couldn’t do it. This time we did, and they did.”

Mr. Blinken and other administration officials insist that Colonel Qaddafi is bleeding money and running out of ammunition and allies, and what’s needed is patience until he is eventually forced out.

They make no secret of the fact that American power is limited by commitments elsewhere. “This is about the president marrying strength and wisdom and applying power in a smart way - at a time that we still have 100,000 troops in Afghanistan, and 47,000 in Iraq,” Mr. Blinken said. In other words, the message to Europe is: Thanks for the invitation, but it’s your neighborhood, your worry about refugees, and primarily your problem.

The caution surrounding Libya grows from a central lesson of America’s decade at war: When the United States is the driving force of a revolution, it owns the outcome, good or bad. No matter how rapidly American troops start withdrawing from Afghanistan this summer, the United States will be there for years; some say decades.

In Libya, the problem is accentuated by the fact that it’s anybody’s guess who will be running the country after Colonel Qaddafi is gone. The case for caution was endorsed in late April by the grandmaster of American diplomacy, Henry Kissinger, who stopped by the State Department for a public rumination with Secretary of State Hillary Rodham Clinton about the changing nature of diplomacy and conflict.

“You cannot judge the outcome of a revolution by the proclamations of those who make it,” Dr. Kissinger warned. “Secondly, those who make it rarely survive the process of the revolution,” meaning that there is usually a “second wave” that can veer off in a different direction - exactly what happened in Iran. And, he concluded, “the greater the upheaval that the revolution causes,” the more likely it is that “a lot of force gets used.”

Mrs. Clinton made a similar point when the Egyptian revolution was evoking enormous enthusiasm worldwide in February, and at the time she was criticized for sounding too pessimistic. But hearing Dr. Kissinger, she noted, “It’s like playing multidimensional chess of an unprecedented scope.

“You’re trying to hold the board,” she said. “You’re trying to figure out how to make the moves, and people are yelling at you from a 360-degree angle.”


By DAVID E. SANGER